....it was not uncommon for a manufacturer to "update" vehicles in stock. Ford did it with medium and heavy trucks. They would send us a new VIN plate and MSO making a 1971 C600 a 1972. This practice stopped in the early 70s. It could be done on a car where the VIN did not identify the year, like a CSX VIN doesn't.
The Cobras sold after 1967 were still "new" cars and were positively 1967 models as they did not meet any of the new for 68 model year federal requirements i.e side marker lamps, emissions, collaspable steering columns and more.
Rick